From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 172D33112AB for ; Fri, 31 Jul 2026 16:00:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785513650; cv=none; b=GV4Cs1M/vFSQtV8zAQiv2i8lM6HyNJGKRFM/vKXNCWa4FdovLe1/MbvjbTdNh3Q6ftaVTeyGOPccYnkQv359G3l8bA/7LHOyrIowrY3pkRadFyPP3nol6RKfertZqGF5j0/9wA0nVYtJpYocez1yVJMLWVa6NYnKPyA8EnyLbI4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785513650; c=relaxed/simple; bh=H4BdWbGA3RWrFfuGbTJYfRbqynPPSmYhYsjE9f/bJm0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DJPHnWE/X8iqUNnAU00Avlb4DRUtlclThl+FBlruBs8y7VI/g4J4m5DJK4RcZgvLX71riOCNdLMbcXuP/wdUm+Eg0qPvN32RVmmW37da+BhvzHqbamwtXe8LTz/dm/yCoghZfCvNzCCSD4RcVBHdKhfjNU+yJkpimoV1iFsvvzc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Tm8J0MSN; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Tm8J0MSN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 455401F00AC4; Fri, 31 Jul 2026 16:00:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785513648; bh=f4/y1vLYrd2mfMSEi6gWLlnqcbGcmhOY+anaH7N8l2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Tm8J0MSNAzrmkNWMWMNQ3OPeDqU2OeTVmThqSfOXW1Ghm+RAIOXKgNmnJsWKmQ8mB B3D6fXT3kFXGg+t1M3pfPfOa3btOhv1MUWUXinZPljaHx2C9Me9K8AbU+WBAc2PDpW BXmK10VtZnFOcK0z3ZeYN7YLDacYqDYS0AR8oZV2pgUskLSwZhu1NWF3q9ZXsXMmCK hlPLRbxEaePhcqLtsJT2N8B9VcVoJ2JRkQIY90xTNgYPABfIdgLatVxX7wZj8AzcCi OuSKydtd2GFXqVjY2+U2Tm23oElS77iKkzz2Kxjnnj0TaU0wNNgR4Do0MQUGqkmrSB bHxxArb2R4fMg== From: Sasha Levin To: stable@vger.kernel.org Cc: Ashutosh Desai , Lyude Paul , Sasha Levin Subject: [PATCH 5.10.y] drm/dp/mst: fix OOB reads in remote DPCD/I2C sideband reply parsers Date: Fri, 31 Jul 2026 12:00:46 -0400 Message-ID: <20260731160046.647386-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026072924-dexterous-hypnotic-2767@gregkh> References: <2026072924-dexterous-hypnotic-2767@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ashutosh Desai [ Upstream commit 1a8f537f5a1eeac941f262fe73078d6b08ba83c0 ] drm_dp_sideband_parse_remote_dpcd_read() reads num_bytes from the raw message and then unconditionally does: memcpy(bytes, &raw->msg[idx], num_bytes); without checking that idx + num_bytes <= raw->curlen. raw->msg[] is 256 bytes; if a malicious or misbehaving MST hub sets num_bytes larger than the remaining payload, the memcpy reads past the received data into whatever follows in raw->msg[]. drm_dp_sideband_parse_remote_i2c_read_ack() has the same flaw (noted with a /* TODO check */ comment since the code was introduced). Fix both functions by using a single combined check (idx + num_bytes > curlen) before each memcpy. Since num_bytes is u8, it is always >= 0, so this strictly subsumes the simpler idx > curlen form and no separate step is needed. Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: # v3.17+ Signed-off-by: Ashutosh Desai Reviewed-by: Lyude Paul [added missing fixes tag] Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260510201733.2882224-1-ashutoshdesai993@gmail.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_dp_mst_topology.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 702ab6148425..32fa058e5f5d 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -859,7 +859,7 @@ static bool drm_dp_sideband_parse_remote_dpcd_read(struct drm_dp_sideband_msg_rx goto fail_len; repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx]; idx++; - if (idx > raw->curlen) + if (idx + repmsg->u.remote_dpcd_read_ack.num_bytes > raw->curlen) goto fail_len; memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_dpcd_read_ack.num_bytes); @@ -895,7 +895,9 @@ static bool drm_dp_sideband_parse_remote_i2c_read_ack(struct drm_dp_sideband_msg goto fail_len; repmsg->u.remote_i2c_read_ack.num_bytes = raw->msg[idx]; idx++; - /* TODO check */ + if (idx + repmsg->u.remote_i2c_read_ack.num_bytes > raw->curlen) + goto fail_len; + memcpy(repmsg->u.remote_i2c_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_i2c_read_ack.num_bytes); return true; fail_len: -- 2.53.0